Molding sheets of wood



Jam. 13, 1942. O K. MICHAELIS- 2,269,634

MOLDING SHEETS OF WOOD Original Filed Oct. 8, 193'].

Patented Jan. 13, 1942 MOLDING SHEETS OF WOOD Karl Michalis, The Hague, Netherlands assignor to Thomas V. Michaelis, New York, N. Y.

Original application October 8, 1937, Serial No.

168,035. Divided and this application Novemher 9, 1937, Serial No. 173,574. In Germany November 14, 1936 2 Claims.

This invention relates to the bending of wood and more especially to novel means for drybending wood panels and the like.

In my patent of the U. S. No. 2,189,078, of which this application is a division, I have disclosed a dry-bending process which comprises preheating uniformly the inner side of substantially the entire part to be bent of an inwardly dry panel so as to build up therein a temperature gradient with the highest temperature on the inner side of said part whereby to render the wood on this inner side compressible, and immediately thereafter and while the wood still retains substantially that temperature, bending the part thus preheated.

The means for thus preheating the wood disclosed in the specification of that patent are heating plates dimensioned to heat not only a point or a narrow zone of the panel, but to uniformly and evenly apply heat to the entire surface of the flat panel part to be bent; for even and uniform preheating of the fiat panel, before I it is bent, is a condition for the perfect performance of the dry-bending process there disclosed.

According to the present invention now the heating plates disclosed in the patent are replaced by a layer of hot gas in direct contact with and extending over the entire inner surface of the panel part about to be bent so as to evenly and uniformly heat the entire surface and the wood layers adjoining it to the temperature at which they become compressible.

The preheating of the wood by means of an extended. hot, dry gas layer, (which of course should not be a burning gas) instead of by means of heating plates, offers great advantages, both in technical and economical respects. The transmission of heat from a metal plate to a wood panel contacting it is always unsatisfactory owing to the insulating effect of the layer of air inevitably preventing perfect contact between the two surfaces which are never altogether plane. In contradistinction thereto heat transmission from a hot gas layer is excellent in view of the perfect contact established between the gas and the wood. Besides this, while wood panels of different length also require heating plates of different size, a gas layer can easily be lengthened by causing a gas current to travel in a continuous current along a wood surface of varying length. Owing to the more perfect heat transmission the bending temperature which is well above the boiling point of water is reached in a fraction of the preheating period required with heating plates. Thus the use of dry, hot gas layers greatly improves the economy of the drybending process.

In the drawing afiixed to this specification and forming part thereof a device embodying my invention is illustrated diagrammatically by way of example in elevation, partly in cross section.

In the drawings:

Fig. 1 is an elevation, partly in cross-section, of a heating and bending device according to this invention, and

Fig. 2 is a perspective view of this device.

Referring to the drawing, I is a rotary mold and 2 is the axle on which the mold is arranged to rotate. The axle is surrounded with a clearance by a pipe 3 for hot gas with a branch pipe 4 for feeding such gas or steam into the interior of the mold, and a plurality of branch pipes '5, 6 opening into the cylindrical mold surface and forming nozzles directing the hot gas against the bottom surface of the panel M to be bent, which is mounted between the side walls of a heating box 1, open on top and equipped with a pipe 8 and exhaustor 9 for the gas. I0 is a pipe in the mold wall serving for the exhaust of the mold heating gas, the mold constituting a side of the heating box. When the panel, gripped by a gripper II on the mold, has been heated up and has become pliable, the mold is rotated, when it will carry the panel along and wind it up.

The mold is here shown as being rotated by means of coil springs l3 acting on lever arms l2 fixed to the mold axle, but any other means, including weighted levers, cranks, motors, etc. may be provided for this purpose. Instead of a cylindrical mold a mold of non-cylindrical and more particularly polygonal section may be used.

In the foregoing specification and the appended claims, the term dry-bending is intended to refer to the bending of inwardly dry panels, as distinguished from the bending of panels which have been rendered pliable by thorough impregnation with moisture, e. g. by boiling and/or steaming; and the term wood panels is intended to include all kinds of blanks, such as boards, strips and the like, composed of wood fibres, including composite materials of wood and a binder, such as plywood.

Various changes may be made in the details disclosed in the foregoing specification without departing from the invention er sacrificing the advantages thereof.

I claim:

1. A device for dry-bending wood panels or the like comprising in combination, a heating chamber open on one side and adapted to be closed on said trough, bending means near one end of said trough and constituting a side of said trough, and means for filling said trough with hot gas adapted to heat the entire inner side of the panel part to be bent to the temperature at which said part becomes sufllciently pliable to allow being bent by said bending means.

KARL Mlcrmiims. 

